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Jeff Bezos, founder of Amazon, was the number one ranked billionaire on the 2018 Forbes list

2. Inherit money

About one third of the people on the Forbes list inherited their money.

That includes seven members of the Walton family, heirs to the Walmart fortune, and Francoise Bettencourt-Meyers, whose family started L'Oreal.

Inheritance is especially important in Europe, where it factored into the fortunes of about half of billionaires, according to analysis of Forbes' 2014 list by the Peterson Institute for International Economics.

There are plenty of reasons why people with a head start maintain their lead.

For one thing, the value of financial assets like stocks and bonds has risen more rapidly than other kinds of assets in recent years.

Those kinds of assets are also often taxed at a lower rate - if they're taxed at all. An academic study last year estimated that 25%-35% of personal taxes are evaded each year by those in the top 0.01%.

3. Be a hedge funder

There were more than 140 people in the finance sector with fortunes greater than $2.5bn on the 2018 Forbes list - more than in any other industry.

Many of them hail from the US, where 25% of billionaires source their riches from finance.

But don't expect to simply rise through the ranks. JP Morgan Chase boss Jamie Dimon is the rare billionaire banker who took that path.

Most financiers entered the billionaire club like people in other industries - by striking out on their own.

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Abigail Johnson, who heads the US money management firm founded by her grandfather, Fidelity Investments, is one of only about 250 women on the Forbes list

And many of the financiers - almost one-fifth of the richest 143 - have ties to a hedge fund.

Of course, if you're set on breaking into the top ranks of billionaires, odds favour those in the tech industry, which claims four of the top 10 spots.

4. Get out of the UK

The number of billionaires in the UK declined last year - one of the only places in the world where that happened, according to Forbes and other surveys.

The fast-growing Asia Pacific region is more fertile territory.

About 29% of the world's new billionaires last year came from the region, according to an annual survey by WealthX, which estimates that there are about 2,750 billionaires globally, a bit more than Forbes.

China alone claimed 29 of the 259 newcomers on Forbes' list - more than any other country.